I came across the following sentence in a text about 俳句 (emphasis, translation and words in square brackets mine):
携帯電話で俳句を送り合って遊ぶ若者もいますし、外国人が日本人以上にすばらしい俳句を表現することもあります。 There are youngsters who play sending haiku to each other's mobile phones, and there's foreigners who can even make up more splendid haiku than Japanese [themselves].
I know that 以上 means "more", "above" and/or "beyond", but as far as I know, 以上 alone functions as an adverb, so I wonder what role is に playing here. Is it just marking 以上 as an adverb (i.e. signaling that 以上 modifies 素晴らしい俳句を表現する), or there is something else going on? Would the sentence be okay if we remove this に altogether?
I opened a related question dealing with the meaning of 以上に itself, please check it out too.